Minimally invasive and full sternotomy in aortic valve replacement: a comparative early operative outcomes

Introduction aortic valve replacement is usually performed through a median full sternotomy (MFS) in our department. Minimally invasive aortic valve replacement (MIAVR) has been recently adopted as a new approach. According to the literature, the superiority of MIAVR is controversial. In this study we report early post-operative outcomes in MIAVR compared with MFS access with reference to blood Loss, wound infections, post-operative recovery, morbidity and mortality. Methods this study was a prospective data collection from 36 consecutive patients undergoing isolated valve replacement. Two population study was identified, MIAVR group (group I n=18) and MFS group (group II n=18). Patients´ data were collected and analyzed using IBM SPSS statistics 21 software and Khi2 test has been used to compare the variables. The study variables are presented as numbers, percentage, median with interquartile range. Pre-operative planning was performed so that to obtain similar characteristics. Results in group I, upper mini-sternotomy was used in 12 patients and right mini-thoracotomy in 6 patients. There was no difference in term of mortality and morbidity. MIAVR was associated with longer CPB time (93.25 (58-161) vs 131 (75-215) mins, P=0.047) with no significant difference in term of ACC time (81 (33-162) vs 58.8 (59-102) mins P=0.158). MIAVR´ Patients had likely lower incidence of red blood cells transfusion (16.7 vs 52.3%) without significant difference about post-operative haemoglobin (P = 0,330). Patients in group I had shorter ventilation time (2.35 (1-12) vs 9.3 (1-48) hours P < 0.01), shorter ICU stay (2.44 (1-8) vs 4.25 (1-9) days, P = 0,024). The length of hospital stay was shorter, 6.5 (5-9) days in group I vs 7.4 (6-11), P=0.0274. Length of chest tube stay was shorter in group I (mean 1.53 vs 2.4 days, P=0,033). Wound infections were not found in both groups. Conclusion minimally invasive aortic valve replacement is associated with less blood loss, faster post-operative recovery faster post-operative recovery but increase operation time.


Introduction
Aortic valve replacement (AVR) through a full sternotomy (FS) is the traditional standard approach in treatment of aortic valve disease [1]. Minimally invasive aortic valve surgery (MIAVS) has been reported with operative benefits while compared with full sternotomy access [2]. However, some studies have not demonstrated a beneficial effect for minimally aortic valve surgery (MIAVS) [3]. The aim of this study was to report early post-operative outcomes in minimally aortic valve replacement (MIAVR) compared with the access by full sternotomy in order to establish the interest of minimally invasive approach. Our study was based on assessment of blood loss, wound infections, post-operative recovery, morbidity and mortality.

Methods
Study design and setting: this study was a prospectively collected data. It was lead in the Cardiovascular Surgery Department at the Mohammed VI university Hospital, Marrakech, Morocco. This department is a reference hospital for cardiovascular surgery in Morocco in which adults and congenital heart surgery are routinely performed. Among the adult patients admitted to this department for heart valve surgery, a total of 36 patients planned for isolated aortic valve surgery were prospectively selected to perform this study. Assessment of blood loss, wound infections, postoperative recovery, morbidity and mortality related to both surgical approaches was performed.
Study population: a critical patient´s selection was used. Our exclusion criteria were emergency cases, patients with aortic root dilation, patients with an unfavorable anatomy, and serious lung disease. Patients requiring concomitant procedures such as coronary artery bypass grafting, or other valves surgery were excluded. The main inclusion criteria were patients with isolated valve replacement. Preoperative planning included clinical assessment, chest X-ray, transthoracic echocardiography (TTE), and electrocardiogram (ECG) assessment. Coronary angiography was done in the patients with heart risks factors. Peripheral femoral doppler was also performed. Pre-operative planning was performed so that to obtain similar population studies between the two groups. There were no statistical differences between both groups in terms of demographic data, cardiac status, and associated pathologies.
Surgical technique: our techniques have been well described in the literature [4][5][6][7][8]. In the group I patients, two different minimally invasive approaches were used in our series: a mini thoracotomy and an upper mini-sternotomy (UMS). About right mini-thoracotomy (RMT), a 4 cm to 6 cm skin incision was placed at the level of the third intercostal space. Five-mm endoscopic trocars were introduced through the fourth and sixth intercostal space at the level of the anterior axillary line; another one in the fifth intercostal space at the level of the middle axillary line in order to perform aortic cross clamping and camera utilization. Femoral-femoral cardiopulmonary bypass (CPB) was performed via a small groin incision. Most cases used mild hypothermia to normothermia CPB. The ascending aorta is clamped with a lowprofile aortic cross clamp and antegrade cold blood cardioplegia is delivered directly. The aortic valve is replaced as usual fashion. The upper ministernotomy (UMS) is achieved through 6 to 10 cm midline vertical skin incision, performing a partial J sternotomy at the third to fifth intercostal space. Standard cannulation of the ascending aorta was performed directly through the incision. Venous cannulation was performed either via the right atrial appendage in many of our patients or with femoro-femoral cannulation. A transverse aortotomy is placed higher. For the group II patients, a full median sternotomy was performed and aortobicaval cannulation for CPB using normothermia in most cases.
Data collection: a prospectively collected data was analysed from November 2017 to October 2019 using IBM SPSS statistics 21 software. The patients were divided into two groups, the group I (n=18) underwent MIAVR and in the group II (n=18) was operated with MFS. The decision to perform MIAVS or FS depended to the surgeons. Peri-operative and 30 days follow-up data were collected and compared.
Definitions: the variables like Length of chest drain stay, intensive care unit (ICU) stay, ventilation time, cardiopulmonary bypass time, aortic cross clamp time, wound infections were appreciated in term of comparison in reference to P value. Blood loss was defined as the difference of pre-operative and postoperative hemoglobin and the incidence of blood transfusion.
Statistics analysis: continuous variables were collected and described by the median with interquartile range, and other variables using their numbers, frequencies and percentages. The data were compared using Khi2 test, P<0.05 is considered statically significant with confidence interval at 95%.
Ethical considerations: individual consent based by oral request was obtained from all patients before the surgery. The patients have been informed about the risks of surgery and the interest of the study.

Results
The following variables are presented as numbers, percentage, median with interquartile range. Preoperative data ( This characteristics baseline did not show significantly difference in the two groups. The mean pre-operative hemoglobin was not different in both groups (13.9 (10.953-15.3) in group I vs 13.4 (7.8-16) g/dl in group II, P=0,444). All the patients underwent AVR; any patient in the MIAVR was required reconversion to full sternotomy. An upper mini-sternotomy approach was used in 12 and six (6) RAMT were performed. One (1) patient received a bioprosthetic valve (bovine pericardial). All procedures were uneventful.
Intraoperative data ( Haemorrhage complications were more likely in the group II than the group I (44.4 vs 16.7%). The incidence of pulmonary complications was similar in both groups. In contrast to the group II, cerebrovascular events in one patient were found in the group I. The length of hospital stay was 6.5 (5-9) days in the group I vs 7.4 (6-11) in group II, P=0.033. In both groups, there was no in-hospital and 30-days mortality.

Discussion
We did not find any difference in term of mortality, morbidity in our series. However, MIAVR was associated with lower incidence of blood loss; shorter mechanical ventilation time, intensive care unit stay, and length of hospital stay compared with the group undergoing full sternotomy. Moreover, faster recovery was associated with MIAVR versus group of FS. The group of FS had a shorter CPB time but not significantly difference in view of aortic cross-clamp (ACC) time. After the first valvular surgery through right thoracotomy under CPB [9], FS approach was adopted as a gold standard and make safely surgical procedures. That conventional approach proved long-term success in aortic and mitral valve surgery [10]. Otherwise MIAVR has been reported with superior benefits while compared with FS access [2]. According to the literature the two surgical procedures can be compared with reference to certain operative variables.
In fact, our series did not show any difference in term of morbidity and mortality. Our observations are consistent with Glauber et al. [11], Del Giglio et al. [12] who showed any difference between MIAVS and FS in term of peri-operative morbidity and mortality. Merk et al. [13] reported the same results but with a higher long-term survival in MIAVS than the group of FS. However, as our series MIAVS is associated with improve early postoperative outcomes compared with FS procedure. Glauber et al. [11], Merk et al. [13] and Bakir et al. [14], reported in their studies that MIAVS is associated with shorter ventilation time, length of hospital stays, lower blood loss. According to Glauber et al. [11], MIAVR performed through RMT, or UMS is a safe procedure associated with excellent postoperative outcomes in terms of mortality, morbidity, shorter hospital stay and faster recovery. In contrast current studies such as the one of Young et al. [15] and Del Giglio et al. [12] showed similar outcomes between both procedures. Particularly Young et al. [15], had concluded through a literature review that benefits are demonstrable, particularly in higher risk, comorbid settings. Brown et al. [16] in metaanalysis had reported that mini-sternotomy can be performed safely for aortic valve replacement, without increased risk of death or other major complication; however, few objective advantages have been shown. Throughout these studies including our study, we can say that minimally invasive (MI) for AVR improves early post-operative outcomes compared with FS access despite some controversy results reported by other studies. Moreover, our series did not find wound infection.
The series of Glauber et al. [11], this study reported that the occurrence of stroke, renal failure, reexploration for bleeding and wound infection was similar in both groups. These complications should not relate to the type of procedure. Compared with FS approach, MIAVR is known to provide faster recovery. In addition, MIAVR has shown to improve post-operative respiratory function due to the preservation of sternum and reduction of post-operative pain, blood loss and blood transfusions related to the reduction of surgical dissection.
In our series FS group had a shorter CPB time but not significantly difference in view of aortic crossclamp time; our observation is consistent with Del Giglio et al. [12] and Merk et al. [13]. The increased operation time in MI approach is reported by many comparative studies. Despite advantages of MIAVR, it is limited by the longer operative time which may compromise operative outcomes in high operative risk patients. According to the literature, suture less valve could be an alternative to reduce operative time in MIAVS and so allows performing minimally invasive safely in high-risk patients [17][18][19]. Our study is limited in term of population size; however, it provides a comparative result with many studies cited above. That makes it consistent with the literature.

Conclusion
Minimally invasive aortic valve replacement is associated with less blood loss, faster postoperative recovery but increase operation time.
Our study confirms that minimally approach can be used safely in aortic valve replacement.

Competing interests
The authors declare no competing interests.

Authors' contributions
All authors have participated to the conception and design, acquisition of data, analysis and interpretation of data; participating in drafting the article or revising it critically for important intellectual content; and gave final approval of the version to be published. Table 1: pre-operative variables and data analysis